Known film changers for radiodiagnostic apparatus include, for example, a supply magazine which is coupled to a mechanism which separates and extracts individual sheets of film from the film stack. The sheets are moved individually to an exposure region where they are placed one by one between two pressure plates which may be equipped with intensifying screens in which the film is exposed to X-radiation after which the film is transported to a receiver for exposed film.
The use of mechanical devices for separately extracting a film sheet from a stack as well as transferring the film to the exposure section and ejecting the exposed film therefrom, involves the use of a plurality of electric motors or, as described, for example, in French Pat. No. 1,571,792 delivered May 12, 1969, using a single motor for controlling the operation of a film sheet changer together with transmission devices (chain and sprockets, belt and pulley, or gearing) for driving a plurality of shafts in rotation and electrically controlled couplers (electromagnetic clutches) whose respective sequential operation has to be controlled by a programmer delivering electrical control signals. This implies relatively complex arrangements whose reliability and maintenance may create problems. The use of several motors or of couplers and transmissions with a single motor also increases the dead weight of the apparatus and makes them cumbersome and difficult to handle. Moreover, the required near-perfect synchronization between the different parts becomes difficult to maintain for relatively rapid rates of frame exposures.
Several known film changers, such as those described in U.S. Pat. Nos. 3,891,850 and 3,971,953 respectively issued June 24, 1975 and June 27, 1976, or in French Pat. Nos. 2,099,303 and 2,196,726 respectively delivered Feb. 14, 1972 and Mar. 4, 1974, make possible the use of film of different formats. A different supply magazine and different extraction and film transfer devices are then required for each format, which still further increases the size and complexity of the apparatus.